40m 1/4 Wave Re-build

I took down and rebuilt the 40m 1/4 wave vertical this past Saturday. I am using the same mast and vertical radiator as before but I have added the radial plate with 20 ground radials. I replaced the coax pigtail with the small vertical junction box I had been using previously. Overall, glad I made these changes as the connections were getting rusty and there was clearly some water getting into the feedline. I will start working to pin the radials down so I don;t have to pick them up when m,owing the lawn. I also plan to put up the 20m vertical element as before so I can have a resonant antenna on 40m, 20m and 15m (3rd harmonic of the 40m). Once the 20m vertical is up I can use it for A vs. B comparisons with the 20m half square. Also looking at a shortened 80m vertical to add to this set of “fanned” verticals.

The 20m Half Square is On the Air

It took several days of off and on work to debug the problems with the EFHW matchbox. I had to disassemble and rewire this several times before finding the issue. I noticed initially that the toroidal inductor seemed sensitive to motion. I ended up completely rewinding the coil then used some hot melt glue to pin down the winding.  Ultimately the problem was with the capacitor. I ended up modifying it so that the capacitance range was maxed out. Seems to be working now and the antenna tuned to 2:1 SWR across all but a small portion of the CW portion of the band. I made some SSB calls and completed the QSO’s however the signal reports were in the 56 to 57 range. I am running WSPR now and will collect some data as a comparison.

Weekend 20m Half Square Experiments or “…Nothing is Ever Easy”

It started off well, I had previously measured the wire 35.4 feet for the horizontal section and 17 feet for the initial cut of the two vertical sections (full wave total wire length for 20m). I used the new longer fishing poles and managed to fit them in the yard. As expected there was significant sag on the horizontal section but was manageable. I hooked up the EFHW matchbox from the linked EFHW project to one end to voltage feed it. It tuned up nicely with a 1m counterpoise:

Going inside the shack I made a few domestic Phone contacts with 55 57 signal reports. I did notice SWR was swinging a bit and started to check on it. That is when the real fun started. Suddenly the SWR lock up very high across the band. I thought there might be a bad antenna switch or loose coax connector. I built another ugly balun. Checked the match box with a 3.9K Ohm resistor and started seeing the weirdness. Sometimes is worked, sometimes it didn’t. I opened it up and checked the connections but couldn’t find a definitive wiring problem. I basically rewired it from top to bottom after checking the capacitor and inductor verifying they still worked. It behaved while I set it up but the minute I stepped back in the shack….sky high SWR. Check just the matchbox and it is not responding. Re-wired it a second time. Pretty much the same behavior.

So I have narrowed it down to the toroid. I may have a subtle solder issue one one end as well as shifts due to movement. I’ll debug this some more this afternoon. So far:

The Good: Easy to setup with potential for good gain.

The Bad: somewhat narrow banded

The Ugly: the EFHW matchbox wackiness tying up most of my antenna time this weekend.

A Quick Radial Experiment

I added about 12 feet to two of the 40m quarter wave radials, trimmed the ends so there is bare copper and dropped then into the resaca in the backyard. For those not familiar with the word “resaca”, it is a type of oxbow lake which in my case was a channel of the Rio Grande River that was cut off from the river and forms no inlet or outlet. The water is fresh but somewhat brackish.

The result appears to be minor. SWR dropped to 1:1 but not sure if it is because of the longer wires or the contact with water.

The Half Square Antenna

I am planning to assemble a 20m Half Square antenna this weekend. The vertical sides will be 17 ft long and separated by 35.4 ft of wire at the top. I am planning to voltage feed this antenna with the EFHW matchbox. I should be able to angle this so that the radiation is at a bearing of 40° for European DX. This configuration should not require any ground radials and promises about 3dB gain over the vertical:

This antenna should be fairly easy to deploy with two fishing poles

DX Century Club

I recieved my DX Century Club Certificate from the ARRL today!

40m FT-8 to Asia Working Again

I have been having good luck working DX into Asia on 40m FT-8 the past few mornings. The opening have lasted here well after sunrise until about 8:30am local time. I have made numerous contacts the past few mornings into Japan, Indonesia & the Philippines. The band had seemed to be shifting but it was likely just poor propagation conditions. Glad to be working these contacts again.

Inadvertently Stress Testing a Homebrew Buddistick

I took out my homebrew Buddistick over the weekend to test its performance versus the full size verticals I have been playing with. I haven’t really deployed this in some time so I was able to make some comparisons to some of the antennas I have been working with lately, namely the 1/4 wave ground mounted verticals. Setup up was about as easy as I remembered it but certainly more complicated than the ground mounted vertical. It is also heavier than I remembered it to be. I had it setup with three guy lines and a single elevated radial and it tuned to 1.46 SWR on the 20m band. On 20m it is not a full size radiator and relies on a small coil to bring it to resonance.

Performance was actually quite good on 20m WSPR. Two days in a row I made the WSPR challenge board. It still remains about 20 spots below the nearby station of N5CEY. The number of spots on 1/2W transmit was about equal to the number of receive spots which I am finding to be a good indicator of antenna efficiency. Thais tells me what I already knew, that is, it is a good QRP field antenna.

The antenna went up Saturday afternoon and stayed up through Monday afternoon. Monday it got breezy here at the QTH. Wind speeds picked up to around 20mph with gusts to 35mph. At some point, the camera tripod failed at the point where the PVC pipe meets the tripod. The whole mess came down hard. Fortunately, the whip was spared any damage and the tripod can be repaired.

For my next trick I am going to try and replace the whip with a fishing pole and wire with an elevated radial. Should be much lighter. It has also proven to be much more resistant to the “valley Wind Machine” that builds up around here this time of year.

A Man with Two Watches is Never Really Sure what Time it is…

I have started to do some testing of the miniVNA I bought from RA0SMS. The software that Anton points to downloaded and installed without issue. I also downloaded jVNA and installed after installing the Java JRE. The first software worked pretty much out of the box. The jVNA software was giving completely bogus results until I realized I had to adjust the DDS factor so that the frequency output is calibrated. Anton recommends a value of 34,354,689 for this which I verified using an oscilliscope.

Once this was setup, the two programs gave largely the same results. I tested a 50 Ohm load, the 40m vertical and the 20m vertical through the miniVNA, RigExpert AA-230 Zoom and the mini60 analyzers. The first thing that showed up was that the SWR & Xs curves have generally the same shape and indicate the location of minimum SWR correctly. The magnitude of the SWR at minimum is not matching up. When I look at the 50 Ohm load data, the RigExpert and mini609 are dead on but the miniVNA is reading several Ohms lower.I am going to have to dig around a bit as I suspect this is a calibration issue.

Update: Google translate does not work to well on Russian…there are some tips on calibration and accuracy on RA4NAL’s website but her’s a sample of the translation “There can be no personal podebarking, because we do not reference and lyubitelsky device for setting the actual antenna instead for pseudo-scientific research. What is the difference when work on the air, if the SWR = 1.1 or 1.05?”

Arrrgh my head hurts!